fix: CNDS2025 talk 2625のスライドURLをSpeakerDeckに修正

短縮URL（red.ht）からSpeakerDeckの直接URLに変更し、
スライド埋め込みが正常に表示されるように修正

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: 2 people

src/data/talks/cnds2025.json

@@ -249,7 +249,7 @@
     "talkDifficulty": "初級者",
     "talkCategory": "Networking",
     "onAir": false,
-    "documentUrl": "https://red.ht/CNDS2025_UDN",
+    "documentUrl": "https://speakerdeck.com/tsukaman/re-noudn-wocan-raemarutitenantomovmtong-he-mosi-inomamaxin-ji-neng-deqie-rituo-kuk8snetutowakunowei-lai",
     "conferenceDayId": 34,
     "conferenceDayDate": "2025-05-23",
     "presentationMethod": "現地登壇"